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Thursday, September 22, 2016

Model Railroading - A Multi-Dimensional Hobby - Part 2


A Multi-Dimensional Hobby - Part 2 - Benchwork

This is the part 2 of a series of articles exploring the changing face of model railroading and how it continues to evolve into a contemporary, varied, fulfilling and exhilarating hobby.

The last article talked about the amazing breadth of the hobby - ranging from research and design, to operations and recreating a segment of history. In this article, we will be looking at the benchwork required for a model railroad.

Benchwork is the foundation, the basic support structure for the model railroad layout. Over the years, different approaches to benchwork have developed. Traditionally, the first step in graduating from simply setting up track on the floor is to a sheet of plywood, framed out in some fashion to prevent sagging, supported by legs. Most common is the classic “4’x8’” sheet of plywood, which provides enough width to make a useable, albeit tight turn and enough width between the turns to allow a little straight run for a few sidings and some scenery. A quick internet search or even paging through some track plan books will generally yield dozens of track plans suitable for the 4x8 tabletop.

Before we go much further on the topic of benchwork, a word about track curve radius is in order. Trains are large, long, moving machines, and on the prototype (full-size), they need a lot of room for making a direction change. A “tight” turn on the prototype is on the order of a 700’ radius, and is generally reserved for industrial spurs. Translating this in to HO scale would require over an 8 foot radius - of course twice that or 16’ diameter for a full turn back! Naturally this is not practical for most layouts. As such, compromises need to be made to allow model trains to be run.

Here we see all three benchwork methods in use. The layout to the left is a conventional table-top construction. It uses two sheets of foam to allow some relief of the scenery by cutting out sections of the foam. Lower right is an example of open grid benchwork. Scenery is able to rise above and below the track.Above that section is an example of classic shelf style benchwork. Shelf brackets support a framework of 1x4 boards and plywood.

Model railroad radii are generally categorized into “sharp,” “conventional” and “broad” curves. The following table summarizes these for some of the most popular scales:

Curve Category O-scale HO-scale N-scale
Sharp 36” or less 18” or less 9” or less
Conventional 48 - 60” 24 - 30” 12 - 15”
Broad Greater than 60” Greater than 30” Greater than 15”

The reason curve radii are important is they define the requirements for the track plan, and consequently, the benchwork. Note for example, a 4’x8’ table top is wide enough to accommodate an 18” radius turn of 180 degrees on each end, with a little to spare (18” - 1’- 6”; since it is a radius, there’s a need for 2X for diameter, or 36” or 3’-0”). Theoretically a 24” radius curve will fit on a 4x8, but keep in mind the radius is measured from the centerline of the track. If a 24” radius will be used, the centerline of the track will fit on the 4x8 plywood, but half the track at the ends will be overhanging the edge of the table.

The other element to be aware of when configuring the track radius is the maximum size of equipment that can be run. If the layout will run short cars and short locomotives, a sharp radius curve standard may not be a problem. There are many logging lines that have been modeled in HO with track radii of 16” or even less. However if the desire is to run long steam or diesel locomotives, perhaps trailing a crack passenger train of 85’ cars, broad curves are in order. There are some longer cars that manufacturers will claim can be run on conventional curves, but keep in mind their operation will likely be compromised (don’t try to back them up!) and they will sure look a lot better on a wider curve.

Generally, track planning and development of benchwork will end up being a compromise between the two. Rare is the model railroader who feels they have all the room they need to run the equipment they want. Make the choices that make sense to you, and stick with them. On that note, many model railroads go so far as to write up standards to assure they don’t compromise their own design. The standards include specifying minimum radius for the layout, maximum length of cars and even required clearances to the edge of benchwork. But all this is fodder for another article.

A variation of the table-top 4x8 is what is called a “cookie cutter” type design. The flat table-top 4’x8’ leaves little opportunity to provide scenic elevation changes and vertical relief to the scene. The cookie-cutter layout concept is to take the same sheet of plywood and cut a pattern into it that will allow segments to be raised or lowered relative to each other. Spacer blocks are provided to support elements of the table relative to others. It might seem minor, but even 2-3 inches of relief remarkably enhances any layout. Note that these pieces do not need to be cut apart. A lobe can be cut into the plywood and raised, allowing for the connecting plywood to create a smooth vertical transition to mount track or roadways between the differing elevations.

There are some notable drawbacks to the table-top design, primary of which is it is a darn big intrusion into a room. A 4x8 requires access all around. The table top is too deep to reach across. Therefore some kind of access is required along the back, even if narrow. This causes the table to protrude even further into the room. This is fine as a small layout in a spare room, perhaps an unused portion of a basement or even garage. But if a larger layout is desired, or if space is at a premium, other options must be considered. After some time with the trusty 4x8 layout, most modelers will move into another design. Enter the shelf layout.

The shelf layout, as its name implies, is set up not unlike a bookshelf would be. Brackets affix to the wall, and some kind of shelf is provided to develop the layout. The shelf can be as narrow or deep as desired, but typically is not less than 6” deep to leave room for scenery, nor is it generally more than 24” deep to allow reasonable access to the back (as well as the practicality of supporting a shelf that deep). The shelving system can be set up around the entire room to create a loop or even spiral if additional run length is desired, or just run along one or two walls. Note that shelf layouts really do not have enough room for a “turn-back” on the shelf itself (unless in the smaller scales). However, the linear design generally allows for a more natural and realistic flow of scenery. Another advantage is the wall immediately becomes available as a backdrop to the layout. Painting of the wall or even photo murals can be used to enhance the visual depth of the model. Similarly, a second shelf can be placed above the layout, provided with a valence, creating a convenient place for adding layout lighting, as well as framing the layout into a visual vignette.

The most flexible approach to benchwork is the development of a true independent structure. These are generally developed using individual pieces of dimensional lumber and plywood. They are pieced together in a lattice framework of legs, joists, risers and track subroadbed. They will also generally incorporate provisions for the support of backdrops and fascia to provide a finished look to the layout. “Open Grid,” as this benchwork is called, allows the modeler to place the tracks anywhere and at any elevation. Scenery can drop below the tracks, or tower above. It is entirely up to the individual. There are many books on the subject and it is worth reading a few of them to gain understanding of the different designs and methods of this benchwork.

Open Grid benchwork is also by far the most complex to develop, however, it is by no means out of the reach of ordinary hobbyists to build. Rather than technical knowledge or craftsman skills, what is required most is patience in working through the details. A quarter-inch vertical off-set may not appear to be much, but will cause significant problems later on when setting the track. That said, it is still easily correctable through the use of shims and sanding. Careful planning, some basic skills with wood, patient assembly of the pieces, and an eye toward the final goal will yield a very satisfying and reliable structure.

The backdrop of a blue sky is constructed of masonite. Above that is a valence of black painted masonite to provide a finished edge. On the front of the layout are signs, control panels, operations paperwork boxes and some shelves for convenience. A masonite facia provides a clean, finished front to the layout.

Before we leave the topic of benchwork, it is worth discussing a little about the actual track support, the “subroadbed.” Track needs to be supported. Additionally this support has to provide a few additional things: it needs to be smooth, without sudden changes in height. It needs to be sturdy enough such that it will not sag, particularly over time. It also needs to provide a means of accepting nails or at least some means of attachment of the track to the sub-roadbed. Traditional plywood has done well for all these elements. Plywood should be at least 3/8” thick, and most modelers prefer 1/2". However plywood is very hard to hammer small track nails into. Additionally with the plywood acting as the bearing surface for the track, the track will be at the same elevation as the scenery. On the prototype, tracks are generally set on ballast, raised above the surrounding terrain. So often a strip of cork is installed over the plywood and before the track is laid. Cork roadbed is sold with a pre-cut edge to mimic the natural slope of the ballast. This provides a realistic elevation to the track, while providing a soft surface to smooth out any irregularities or gaps. Besides cork, some modelers prefer a paper-board product called Homosote®. This accepts nails quite readily and has the added advantage of deadening sound. A relatively new option is the use of insulating foam sheets (the solid sheet type, not the white beaded type) for both subroadbed and roadbed. It provides a lighter structure and is easily cut and shaped. Attachment of the track can be by conventional track nails, scale spikes or even wire brads. Some modelers prefer their track to be attached with caulk or other non-solvent based glue to get rid of any evidence of oversized nailheads when the layout is complete.

Each of the benchwork and track subroadbed styles have their own best application and advantages. Often multiple methods will be used in developing a layout. For example, there may be a peninsula in the room using the open grid benchwork; tracks will run along the wall using a shelf system, and a yard area perhaps will use a conventional table-top method. Feel free to adjust the designs to suit the need.

Benchwork may appear to be a daunting element of model railroading. However, it is really is not that difficult and can even be fun to develop. Different approaches and designs allow it to be adjusted to meet the needs of the layout. While there are some design and construction considerations that need to be made, the work is well within the capability of any individual interested in doing so. And once completed, you will be ready to move into the next phase of building the layout - laying track!

Author: Detlef Kurpanek

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